How to grow black eyed susan vine
Overview
Black eyed susan vine (Thunbergia alata) is a fast-growing, twining climber from tropical Africa, grown for its cheerful orange-yellow flowers with dark centres. It is ideal for softening fences, trellises, and pergolas, and can be grown as a trailing plant in hanging baskets. It thrives in warm, humid conditions and is often treated as an annual in cooler climates.
Varieties
- Thunbergia alata 'Orange Wonder' — Vigorous orange-flowered form, popular for quick coverage in warm gardens.
- Thunbergia alata 'Sunny Lemon' — Pale yellow flowers with a dark eye, ideal for hanging baskets.
- Thunbergia alata 'African Sunset' — Deep orange blooms with a red-brown centre, good for trellis.
Soil Preparation
Prefers a slightly acidic to neutral pH (6.0–7.0) in fertile, well-drained soil. Enrich with well-rotted manure or compost before planting. If soil is heavy clay, improve drainage with coarse sand or grow in a raised bed.
Growing Guide
Plant in a position with bright, indirect light and protection from harsh afternoon sun. Space plants 30–45 cm apart at the base of a support. Use well-draining soil enriched with compost, and keep the root zone consistently moist but not waterlogged. Train new growth onto a trellis or wire frame as soon as stems appear. In cooler zones, wait until soil temperature reaches at least 18°C before planting out.
Sowing
Sow seeds 1 cm deep in seed-raising mix, 2–3 seeds per pot, and keep at 20–25°C. Germination takes 10–14 days. Transplant seedlings after the last frost when they have 2–3 true leaves. Soak seeds overnight to improve germination.
Care
Feed monthly with a balanced liquid fertiliser (e.g., 10-10-10) during the growing season. Prune back spent stems after flowering to maintain shape and encourage new growth. Train tendrils onto supports weekly to keep the plant tidy and promote dense coverage.
Companion Planting
Pair with other warm-season climbers like morning glory or jasmine for a layered vertical display. Avoid planting near heavy feeders such as sweet corn or pumpkins, which may compete for nutrients. Good light screen plant for shading south-facing walls.
Common Pests & Risks
Aphids and whitefly can cluster on new growth; spray with a dilute soap solution or neem oil. Spider mites may appear in dry conditions; increase humidity by misting or hosing foliage. Check for caterpillars that can strip leaves and treat with Bacillus thuringiensis if needed.
Troubleshooting
Yellow leaves: often from overwatering or poor drainage; let soil dry slightly between waterings. Brown leaf edges: caused by low humidity or dry air; mist regularly or move to a more humid spot. Stunted growth: check for root-bound pots or insufficient light; repot or shift to brighter position. Flowers dropping: sudden temperature changes or water stress; maintain consistent conditions. Sparse foliage: lack of support or pruning; train stems and pinch tips to encourage branching.